Gross machine moisture control system for the net end of a paper machine

ABSTRACT

This invention relates to wet end moisture control utilized in the making of a continuous web of paper. An on line cross machine moisture profile is obtained and this profile is automatically adjusted by appropriately changing the relative contributions of a plurality of control actuators so that the profile is made to conform more accurately to a desired shape prior to entering the dryer section of the paper making machine. A scanning moisture gauge traverses the web between a press roll section and the dryer section. From this scan, a continuous moisture profile is stored from which the gross moisture level, skew, and curvature of the profile are computed. From gross moisture level, skew, and curvature signals, the control actuators simultaneously apply controlled amounts of pressure to the ends and center of the press rolls to bring the continuous moisture profile to a desired profile.

United States Patent [72] Inventor Marion A. Keyes, IV 3,490,689 l/l970 Hart et al l62/252 X South Beloit, OTHER REFERENCES 1969 Britt, K. W. Handbook of Pulp and Paper Technology" Patented Nov. 9,1971 Reinhold Pub.Co. (New York, 1964) p. 384- 385. [73] Assignee Beloit Corporation Primary Examiner-S. Leon Bashore B l ig, wi Assistant Examiner-Alfred DAndrea, Jr.

AtlarneyDugger, Peterson, Johnson & Westman [54] GROSS MACHINE MOISTURE CONTROL SYSTEM FOR THE NET END OF A PAPER MACHINE I I ABSTRACT: This invention relates to wet end moisture con- 12 Claims, 2 Drawing Figs.

trol utilized in the making ofa continuous web of paper. An on [52] US. Cl 162/252, Cross machine moisture fil is obtained and this fil 34/43, 162/198, 162/263 is automatically adjusted by appropriately changing the rela- [5 l I Int. Cl fi t ib ti f lit f nactuators so th t th Field of Search l62/252, profile is made to conform more accuratdy to a desired Shape 198i 34/l4- H6; [00/] prior to entering the dryer section of the paper making machine. A scanning moisture gauge traverses the web [56] References cued between a press roll section and the dryer section. From this UNITED STATES PATENTS scan, a continuous moisture profile is stored from which the 2,738,663 3/1956 Moore l0O/l70X gross moisture level, skew, and curvature of the profile are 2,922,475 l/l960 Alexander.. 162/252 computed. From gross moisture level, skew, and curvature 3,040,807 6/l962 Chope l62/252 signals, the control actuators simultaneously apply controlled 3,1 l9,324 l/l964 Justus /170 amounts of pressure to the ends and center of the press rolls to 3,215,592 ll/l965 Justus et al 162/252 bring the continuous moisture profile to a desired profile.

PRESS SECTION FRONT LOAD DESIRED PROFILE n4 b 4c SUPPLY 955mm c l|2u 2 X SUMMER DESIRED A IM n4 6 0 l0 DESIREDmM w :04 ACTUAL A/ 98b 68 l "2 b" CONTROLLER J I w loo I08 m b IOI 70 70b 92 02c\ ACTUAL A| 82 8o a CONTROLLER A y I02" I020 82!) 82 W GROSS MACHINE MOISTURE CONTROL SYSTEM FOR THE NET END OF A PAPER MACHINE BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates generally to the making of paper in the form of a continuous web, and pertains more particularly to a system for controlling the amount of moisture contained in the web at a location ahead of the dryer section.

2. Description of the Prior Art Various attempts have been made to control the moisture content of a paper web during the making thereof. For the most part, such attempts have dealt with the control of the amount of steam delivered to the drying rolls. However, it is generally recognized that resort to heat energy, particularly where it is utilized for the sole control of the drying procedure, is relatively costly and the mechanical removal of water is substantially more economical. Hence, certain earlier attempts have related to the employing of suction rolls in the press section. The last-mentioned schemes do not take into account that considerable variations can occur in the moisture content of the web as measured transversely across its width. In other words, the cross machine moisture profile, as it is termed, when plotted will possess peaks and valleys. The actual moisture profile may differ quite radically from a desired profile shape.

In U.S. Pat. No. 3,040,807 granted on June 26, 1962 to Wilbert E. Chope for MOISTURE BALANCE CORRECTION SYSTEM, a plurality of heat lamps are controlled in accordance with discrete sections of the moisture profile. Because the patent considers the profile curve to be made up of discrete segments of a fixed level, the patented system does not automatically achieve an optimum estimate of the profile.

SUMMARY OF THE INVENTION The present invention has for a principal object the control of the on line cross machine moisture profile so that it more accurately resembles a desired moisture profile. In this regard, an aim of the invention is to approximate a continuous curve representative of the moisture profile by a polynomial and then controlling the characteristics of the profile by controlling the value of the coefficients of the described polynomial.

Another object is to control the moisture content of a continuous paper web or sheet.

Another object of the invention is to provide a moisture control that is efficient, removing water from the web at the wet end ofthe paper making machine rather than in the drying section where the cost of heat energy is quite appreciable.

A further object of the invention is to provide a moisture control system that will lend itself readily to incorporation into existing paper making machines. More specifically, the invention has for an aim the adjustment of the amount of mechanical loading applied to the upper and lower press rolls in conforming the actual cross machine moisture profile to an optimum moisture profile.

Still further, the invention has for an object the provision of a moisture control system that will be inexpensive to make and install.

Briefly stated, the invention involves the employment of a scanning moisture gauge that traverses the width or trim of the paper web at a location intermediate the press and drying sections. Each time that a traverse pass has been completed, the information or data picked up or sensed by the moisture gauge is stored, and from the stored data, signals are computed which are representative of a finite number of profile indices. If the profile indices derived from the moisture gauge do not correspond with the profile that is desired, then corrective action is taken by adjusting the various control actuators, these actuators in the exemplary situation changing the mechanical loading applied to the upper and lower rolls comprising the press section. The end result as far as the cross machine moisture control is concerned is that the actual moisture profile is caused to fit more closely the optimum profile, use of the least squares principle assuring the most probable approximation.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective diagram illustrating a portion of a typical paper making machine with a wet end moisture control system embodying my invention schematically superimposed thereon, and

FIG. 2 depicts a typical cross machine moisture profile with moisture in percent plotted against trim or width of the web, the profile being taken at a location between the press and drying sections of the fragmentarily depicted machine of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT The paper making machine illustrated in FIG. 1 and designated by the reference numeral 10 is of conventional construction. Accordingly, only those sections of the machine 10 that are needed for describing the present invention will be referred to. First, it will be noted that the paper web as it comes from the Fourdrinier wire (not shown) has been given the reference numeral 11. The web 11 is directed to a press section 12 comprising an upper roll 14 and a lower roll 16, the two rolls forming a nip therebetween.

Inasmuch as one form of the present invention envisages a controlled loading on the rolls l4, 16, the general arrangement illustrated in U.S. Pat. No. 3,119,324 may be employed, this patent being issued to Edgar J. Justus on Jan. I8, 1964 and assigned to the present assignee. In this regard, the upper roll 14 has a shaft 18 which is journaled in a pair of bearings 20. The lower roll 16 has a shaft 22 that is similarly journaled in bearings 24. However, the bearings 20 are individually acted upon in a vertical direction to change the applied load of the ends at the roll 14, whereas the lower bearings 24 are mounted on a fixed surface. Although any number of such shoes may be employed within the lower roll 16, such as the number appearing in the aforesaid patent, nonetheless only one such shoe labeled 26 appears in FIG. 1, the function ofthe shoe 26 being to control the amount of crown imparted to the lower roll 16.

An actuator 28, which can take the form of the fiuid pressure device utilized in the aforesaid patent, is used to vary the loading at the front side of the press section 12 and a similar actuator 30 is utilized to vary the load at the back side of the press section. The actuator for controlling the crown of the lower roll 16 has been labeled 32. The signals supplied to the actuators 28, 30 and 32 will be described hereinafter. However, it will be perhaps of some benefit to explain at this stage of the description that the signals forwarded to the actuators 28, 30 and 32 are such as to cause the press rolls [4 and 16 to provide a cross machine moisture profile that corresponds generally to a desired moisture profile.

The paper making machine 10 further includes a drying section denoted generally by the reference numeral 34. The section 34 in the exemplary situation includes three heated rolls 36, 38 and 40.

Intermediate the press section 12 and the drying section 34 is located a moisture gauge 42 of the scanning variety, the double-headed arrow 44 indicating the path that the gauge 42 traverses. The particular type of gauge is not critical to a practicing of the invention. For instance, it may be of the microwave variety in which energy is absorbed by the water to provide a signal indicative of the moisture content of the web 11. Also, the means for mounting the gauge 42 for scanning movement across the web 11 is not important. Although the gauge itselfdiffers in U.S. Pat. No. 3,007,052 granted Oct. 3 l. 1967 to Hickman et al. the traversing mechanism can be the Same or similar thereto. Since it is contemplated that the moisture gauge 42 will make one scan and then remain stationary before moving back across the web 11, the data that is picked up by the gauge 42 is recorded or stored in a storage means designated by the reference numeral 46. This storage means 46 simply provides output signals that are representative of the past history of what the gauge 42 has sensed, that is the amount of moisture detected at various points as it traverses the web 11, passing from the'front to the back and vice versa.

Reference should now be made to FIG. 2 in which a curve 50 has been plotted that is representative of actual profile information stored in the means 46. lt will be pointed out that the curve 50, this being a typical cross machine moisture profile, has moisture in percent plotted as the ordinate and the distance across the web or trim plotted as the abscissa. It is this curve or profile 50 that is corrected for or adjusted when practicing the teachings of the instant invention. The system for making such a correction will now be described.

Therefore, reverting again to FIG. 1, the system there illustrated for controlling the cross machine moisture in practice has been designated generally by the reference numeral 60. Before describing the control system 60 in detail, it perhaps will be helpful to preface such a description by stating that the exemplary circuitry is intended to provide a finite number of profile indices or coefficients that collectively correspond to the profile characteristics derived via the gauge 42. in other words, the signals that are developed in the system 60 simulate the configuration of the curve 50 and allow comparison with signals that correspond to a desired profile so that correction can be made in the loading applied to the rolls 14 and 16 of the press section 12. A detailed mathematical development will be presented hereinafter involving the principle of least squares that provides the best fit or correspondence of the actual profile to an optimum or desired profile.

Accordingly, the control system 60 contains a multiplier 62 and an integrator 64, the multiplier in this instance multiplying the integral from the integrator 64 by a factor of two. The input to the multiplier 62 is obtained directly from the storage means 46; this input signal is indicative of the moisture sensed by the gauge 42 during its preceding scan. The output signal from the integrator 64 will be called 1 and is forwarded over a line 66 to a multiplier 68 that multiplies the 1,, signal by l.l25/T where T is the trim width, that is the width of the web 11 as measured form front to back.

At this time, attention is directed to another multiplier 72 that has a pair of input terminals 72a, 72b and an output terminal 720. The two input terminals 72a, 72b are connected to the storage means 46 and derive therefrom signals indicative of the position of the gauge 42 in correlation to the amount of moisture sensed. The output signal from 720 is multiplied by a factor of two through the agency of a multiplier 74 and the integral signal 1, derived therefrom by an integrator 76 and is forwarded over a line 78 to a multiplier 80 that simply acts upon the signal 1, by multiplying it by 6/T. The signal from the multiplier 80 is then fed to an operational amplifier 82 having a single input terminal 82a and an output terminal 82b.

The system 60 now being described additionally includes a multiplier 84 having a pair of input terminals 84a, 84b and an output terminal 840 which takes the gauge position signal from the storage means 46 and multiplies it by the output signal from the multiplier 72. The signal thus provided at the output 840 is supplied to a multiplier 86 that multiplies the signal by a factor of two and an integrator 88 provides an integral signal labeled 1, which is advanced over a line 90 to one multiplier 92 that multiplies the 1 signal by a 7.5/T", the multiplied signal being impressed upon the input terminal 70b of the operational amplifier 70.

At this time, attention is directed to a multiplier 94 that accepts the T,, signal and multiplies it by 9(l/T and this multiplied signal is forwarded to an operational amplifier 98, more specifically its input terminal 980. The amplifier 98 has a second input-terminal 98b and this particular input receives a multiplied signal from a multiplier 96 which is connected to the line 90 so as to multiply the signal 1, by 7.5/T The amplifier 98 has an output terminal 980, the function of which will be presently described.

Although more readily apparent from the mathematical development hereinafter presented, it should be noted that the operational amplifier 70 provides at its output terminal 70c a signal A which is related to the gross moisture level determined by the moisture gauge 42. The higher the moisture, the greater will be the signal A,,. From HO. 2, the signal A,, will be seen as being the amount of moisture at X=0, that is the centerline of the web 1 1.

The amplifier 82 at its output terminal 82c provides a signal A, which is related to what will be termed skewness of the cross machine moisture profile. 1f the profile is tilted down on the front of the web 11, the signal A, will be positive, whereas if the profile is tilted down in back, then A, will be negative.

The amplifier 98 provides a signal A which is a measure of the profile curvature. If the signal A is positive, the profile is characterized by a minimum, whereas if the signal A, is negative, the profile curvature has a maximum curvature.

Recapitulating at this point, it should be appreciated that the control system 60 provides signals A,,, A, and A, which are measures of the web moisture profile. While these signals are actual coefficients representing variables constituting the moisture profile, they have not as yet been compared with similar signals representing the desired moisture profile.

Accordingly, a source or supply of desired profile coefficient signals has been denoted by the reference numeral 100. A first summing junction 101 has one input terminal 101:: connected to the output terminal 700 of the amplifier 70, its other input terminal 101b having impressed thereon the desired value of A provided by the profile supply 100 that should be achieved. In other words, the input terminal 101!) provides a set point signal that is compared with the actual signal coming in at the input terminal 101a, and a difference or error signal then appears at the output terminal 1010 of the summingjunction 101.

Similarly, a summing junction 102 has one input terminal 102a connected to the output terminal 82b of the amplifier 82 and its second input terminal 1021) connected to the signal source 100 that provides a desired value for the signal A,. Comparison is made by the summing junction 102 so that the difference or error existing between the actual signal A, and the desired signal A, will be reflected at its output 102C.

Still further, a summing junction 104 has its first input terminal 104a connected to the output terminal 98c of the amplifier 98 and its second input terminal l04b connected to the source 100 that provides a desired value of the signal A the difference appearing at the output terminal 104( of the junction 104.

What has been made available at this point are signals that can be used for controlling the loading applied to the press rolls l4 and 16. In this regard, the overall press loading that is applied to the rolls l4 and 16 by means of all three actuators 28, 30 and 32 will affect the actual signal A, at the output terminal 82b of the amplifier 82. The crown control, this being the loading derived from the actuator 32, will affect the actual signal A, at the output terminal 98c of the amplifier 98.

To make use of the difference or error signals appearing at the several output terminals '10lc, 102s and 1040 are controllers labeled respectively 106, 108 and 110. The controller 106 has connected thereto a multiplier 112 having a first input terminal 112a and a second input terminal 112b, the product signal appearing at its output terminal 112C. The controller 106 is connected directly to the input terminal 112a and directly to a summer 114 having a pair ofinput terminals 114a and 1141; and an output terminal 1140. The controller 106 processes a signal that is essentially in accordance with the total loading that should be applied to the rolls 14. 16. However, it is necessary to derive a ratio of front to back loading and this is done by taking the signal from the controller 108 which reflects what is derived from the A, signals and impresses the resulting signal onto the input terminal 1l2b so that it is multiplied with the signal delivered to the other input terminal 112a. The produce signal from the output terminal 112: is fed not only to the previously mentioned actuator 28,

but also to the other input terminal 114b of the summer 114. it is the signal provided at the output terminal 1140 that is transmitted to the actuator 30.

Especially as can be seen from the mathematical development appended hereto, the data obtained through the agency of the moisture gauge 42 is processed so as to provide polynomial coefficient signals that are representative of the actual cross machine moisture profile. These signals, which represent the actual profile, are compared by means of the various summing junctions 101, 102 and 104 with signals that collectively represent the desired or optimum cross machine moisture profile with the consequence that any differences are utilized, in the illustrative instance, for controlling the pressure exerted by the press rolls 14, 16 against the web 11 passing therebetween. It will be appreciated that the operation is exceedingly simple, for if more water should be squeezed from the web 11 at the front side of the web, this being the side or edge nearer the viewer in FIG. 1, then the pressure must me correspondingly increased there and concomitantly decreased at the back side of the web 11. it will be recalled that a ratio is provided by reason of the multiplier 112 and the summer 114.

On the other hand, if more moisture should be removed from the center of the web, then the signal from the controller 110 will simply cause the actuator 32 to exert a greater upward pressure which can be done in concert with an increased downward pressure applied via the actuators 28, 30. The end result is that the profile represented by the curve 50 in FIG. 2 can be modified to whatever degree is necessary to cause such a curve or profile to conform more accurately to an ideal or optimum profile. Since the water that should be removed is removed only slightly in advance of the location at which the moisture is actually sensed, it follows that there is a minimum amount of dead time involved and that a more accurate profile can be realized in practice. Hence, any drying that must be done by the drying section 34 in order to even more precisely reach the optimum drying condition will be lessened. Hence, both overdrying and underdrying can be obviated so that a high-grade paper product is produced.

The mathematical derivation for the signals A A, and A using the Lengendre principle of least squares to provide the best fit for f(x) is as follows when:

(when I =min) Summarizing: (Normal equations) where Solving for coefficients by Grantor's Rule:

T T" T I T" 1 '1" Consequently, it will be recognized that the desired moisture profile is characterized by the overall curve characteristics-not by discrete sections of the curve. In other words, the system herein described control characteristics of the profile independent of location. For instance, one of the indices A, relates to the skewness of the profile, that is the ratio of the front to back loading in the illustrated embodiment, which has nothing to do with physical location along the profile. The indice A utilized to control the crown, likewise pertains to the shape of the profile, this one being concerned with the relative curvature thereof and having nothing to do with a particular section of the curve. A employed in the overall press loading, is related to gross or absolute moisture level. The three coefficients A,,, A, and A are each determined from on line data and the general shape of curve 50 in FIG. 2 is approximated by the algebraic polynomial: A,,+A,x +Az 2u.

lclaim:

1. In a machinefor making a continuous web of paper, a cross machine moisture control system comprising means providing a plurality of first signals generally indicative of a first finite number of indices which collectively represent a first continuous curve having characteristics corresponding to a desired web moisture profile, means providing a plurality of variable second signals generally indicative of a second finite number of indices which collectively represent a second continuous curve having characteristics corresponding to the actual moisture profile of said web, means for comparing each of said first signals with a corresponding signal from said second signals, means for removing varying amounts of moisture from said web at transverse locations thereacross to change the magnitude of said second signals, and means for controlling said moisture removing means in accordance with any differences with said respective compared signals to change the characteristics of said second curve so that said actual moisture profile more closely approximates that of said desired moisture profile, said first signals including three individual signals which collectively approximate three terms of an algebraic polynomial representing gross moisture level, skew, and curvature of said desired moisture profile, and said second signals including three individual signals which collectively approximate three terms of an algebraic polynomial representing gross moisture level, skew, and curvature of said actual moisture profile.

2. The combination set forth in claim 1 in which said controlling means includes means for adjusting said moisture removing means so that all three second signals are simultaneously varied to change the shape of said actual moisture profile to approximate that of said desired moisture profile.

3. In a machine for making a continuous web of paper, the machine including a moisture removing means comprising a wet press section having upper and lower rolls and a drying section, a cross machine moisture control system comprising first, second and third means for providing a first group of signals generally representative of the actual web profile present at a location between said sections, fourth means providing a second group of signals representative ofa desired moisture profile, means for comparing said first group of signals with said second group of signals, and means controlled by said first, second, third and fourth means responsive to any error signals produced by said comparing means for relatively adjusting said upper and lower press rolls to remove moisture from said web so as to cause said actual moisture profile to conform more accurately to said desired moisture profile, said first means providing a first signal in said first group of signals relating to actual gross moisture level and said fourth means providing a first signal of said second group relating to desired moisture level, said second means providing a second signal in said first group of signals relating to the skew of the actual profile and said fourth means providing a second signal of said second group of signals relating to the skew of the desired profile, and said third means providing a third signal of said first group of signals relating to the actual profile curvature and third signal of said second said fourth means providing a group of signals relating to the desired profile curvature.

4. The combination set forth in claim 3 in which said first means includes a scanning moisture gauge for traversing the width of said web at a location intermediate said press and drying sections.

5. The combination set forth in claim 3 in which said com paring means includes first, second and third summing junctions, said first summing junction comparing said first signals, said second summing junction comparing said second signals, and said third summing junction comparing said third signals.

6. The combination set forth in claim 5 including a first controller connected to the output of said first summing junction, a second controller connected to the output of said second summing junction and a third controller connected to the output of said third summing junction, said moisture removing means being controlled by said controllers.

7. The combination set forth in claim 6 including means connected to said first and second controllers for providing a pair of signals having an inverse relationship with respect to each other, said moisture removing means including a pair of actuating mechanisms for controlling the adjustment of said upper and lower press rolls predominantly on the marginal portions of the web, and means connected to said third controller for providing an additional signal, said moisture removing means including an additional actuating mechanism for controlling the adjustment of said upper and lower press rolls predominantly on the central portion of said web, said pair of signals and said additional signal collectively causing said pair of and additional actuating mechanism to remove moisture in a cross machine direction so that the actual profile more closely approaches a desired profile.

8. The combination set forth in claim 7 in which said pair of actuating mechanisms apply controlled amounts of pressure to the opposite ends of said upper roll and said additional actuating mechanism applies a controlled amount of pressure to the central portion of said lower roll.

9. in a machine for making a continuous web of paper, a

cross machine moisture control system comprising means for removing moisture from said web, first, second and third means for providing a first group of three signals generally representative of the actual web moisture profile, said first means providing the first signal of said first group relating to actual gross moisture level, said second means providing the second signal of said first group relating to the skew of the actual profile and said third means providing the third signal of said first group relating to the actual profile curvature, means for providing a second group of three signals generally representative of a desired moisture profile, the first signal of said second group relating to a desired gross moisture level, the second signal of said second group relating to the skew of the desired profile and the third signal of said second group relating to the desired profile curvature, first means for comparing the first signal of said first group with the first signal of said second group to provide a first error signal representative of any difference therebetween, second means for comparing the second signal of said first group with the second signal of said second group to provide a second error signal representative of any difference therebetween, third means for comparing the third signal of said first group with the third signal of said third group to provide a third error signal representative of any difference therebetween, and means responsive to said first, second and third error signals for controlling said moisture removing means in accordance with the respective values ofsaid error signal.

10. The combination set forth in claim 9 in which said means for controlling said moisture removing means includes first, second and third actuators, means for multiplying said first and second error signals to provide a product signal for controlling said first actuator, means for adding said first error signal and said product signal to provide a summed signal for controlling said second actuator, and means for delivering said third error signal to said third actuator for controlling said third actuator.

11. The combination set forth in claim 10 in which said moisture removing means includes a pair of press rolls between which said web passes, said first and second actuators controlling the pressure applied to the ends of said press rolls and said third actuator controlling the pressure applied to said press rolls intermediate the ends thereof.

12. In a machine for making a continuous web of paper the machine including means for removing moisture from said web, a cross machine moisture control system comprising first, second and third means for providing first signals generally representative of the actual web moisture profile present at a given web location, fourth means providing second signals representative of a desired moisture profile, means for comparing said first signals with said second signals, and means controlled by said first and second means responsive to any error signals produced by said comparing means for relatively adjusting said moisture removing means to remove moisture from said web so as to cause said actual moisture profile to conform more accurately to said desired moisture profile, said first signals constituting a group of three signals and said second signals constituting a group of three signals, said first means providing the first signal of said first group relating to actual gross moisture level and said fourth means providing the first signal of said second group relating to desired moisture level, said second means providing the signal of said first group relating to the skew of the actual profile and said fourth means providing the second signal of said second group relating to t e skew of the desired profile,

and said third means providing the third signal of said first group relating to the actual profile curvature and said fourth means providing the third signal of said second group relating to the desired profile curvature.

3 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent 3.619.359 DatedNovember 9 1971 Inventor(s) Marion A. Keyes, ,IV

It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 3, line 68, "T should be I Column 6, line 18 fin third set of equations, "2701 shoul be 270I line 46,

"+A X should be --+A X Column 7,' line 31, 7 after "and" insert said fourth means providing a--; same line, after "second" delete "said fourth means providing a". Column 8 line 28 "signal' should be signals; line 45, after "paper" insert Signed and sealed this 9th day of May 1972.

(SEAL) Attest:

EDWARD M.FLE'1'OHER,JR'. ROBERT .GOTTSCI IALK At testing Officer Commissioner of Patents 

2. The combination set forth in claim 1 in which said controlling means includes means for adjusting said moisture removing means so that all three second signals are simultaneously varied to change the shape of said actual moisture profile to approximate that of said desired moisture profile.
 3. In a machine for making a continuous web of paper, the machine including a moisture removing means comprising a wet press section having upper and lower rolls and a drying section, a cross machine moisture control system comprising first, second and third means for providing a first group of signals generally representative of the actual web profile present at a location between said sections, fourth means providing a second group of signals representative of a desired moisture profile, means for comparing said first group of signals with said second group of signals, and means controlled by said first, second, third and fourth means responsive to any error signals produced by said comparing means for relatively adjusting said upper and lower press rolls to remove moisture from said web so as to cause said actual moisture profile to conform more accurately to said desired moisture profile, said first means providing a first signal in said first group of signals relating to actual gross moisture level and said fourth means providing a first signal of said second group relating to desired moisture level, said second means providing a second signal in said first group of signals relating to the skew of the actual profile and said fourth means providing a second signal of said second group of signals relating to the skew of the desired profile, and said third means providing a third signal of said first group of signals relating to the actual profile curvature and said fourth means providing a third signal of said second group of signals relating to the desired profile curvature.
 4. The combination set forth in claim 3 in which said first means includes a scanning moisture gauge for traversing the width of said web at a location intermediate said press and drying sections.
 5. The combination set forth in claim 3 in which said comparing means includes first, second and third summing junctions, said first summing junction comparing said first signals, said second summing junction comparing said second signals, and said third summing junction comparing said third signals.
 6. The combination set forth in claim 5 including a first controller connected to the output of said first summing junction, a second controller connected to the output of said second summing junction and a third controller connected to the output of said third summing junction, said moisture removing means being controlled by said controllers.
 7. The combination set forth in claim 6 including means connected to said first and second controllers for providing a pair of signals having an inverse relationship with respect to each other, said moisture removing means including a pair of actuating mechanisms for controlling the adjustment of said upper and lower press rolls predominantly on the marginal portions of the web, and means connected to said third controller for providing an additional signal, said moisture removing means including an additional actuating mechanism for controlling the adjustment of said upper and lower press rolls predominantly on the central portion of said web, said pair of signals and said additional signal collectively causing said pair of and additional actuating mechanism to remove moisture in a cross machine direction so that the actual profile more closely approaches a desired profile.
 8. The combination set forth in claim 7 in which said pair of actuating mechanisms apply controlled amounts of pressure to the opposite ends of said upper roll and said additional actuating mechanism applies a controlled amount of pressure to the central portion of said lower roll.
 9. In a machine for makinG a continuous web of paper, a cross machine moisture control system comprising means for removing moisture from said web, first, second and third means for providing a first group of three signals generally representative of the actual web moisture profile, said first means providing the first signal of said first group relating to actual gross moisture level, said second means providing the second signal of said first group relating to the skew of the actual profile and said third means providing the third signal of said first group relating to the actual profile curvature, means for providing a second group of three signals generally representative of a desired moisture profile, the first signal of said second group relating to a desired gross moisture level, the second signal of said second group relating to the skew of the desired profile and the third signal of said second group relating to the desired profile curvature, first means for comparing the first signal of said first group with the first signal of said second group to provide a first error signal representative of any difference therebetween, second means for comparing the second signal of said first group with the second signal of said second group to provide a second error signal representative of any difference therebetween, third means for comparing the third signal of said first group with the third signal of said third group to provide a third error signal representative of any difference therebetween, and means responsive to said first, second and third error signals for controlling said moisture removing means in accordance with the respective values of said error signal.
 10. The combination set forth in claim 9 in which said means for controlling said moisture removing means includes first, second and third actuators, means for multiplying said first and second error signals to provide a product signal for controlling said first actuator, means for adding said first error signal and said product signal to provide a summed signal for controlling said second actuator, and means for delivering said third error signal to said third actuator for controlling said third actuator.
 11. The combination set forth in claim 10 in which said moisture removing means includes a pair of press rolls between which said web passes, said first and second actuators controlling the pressure applied to the ends of said press rolls and said third actuator controlling the pressure applied to said press rolls intermediate the ends thereof.
 12. In a machine for making a continuous web of paper, the machine including means for removing moisture from said web, a cross machine moisture control system comprising first, second and third means for providing first signals generally representative of the actual web moisture profile present at a given web location, fourth means providing second signals representative of a desired moisture profile, means for comparing said first signals with said second signals, and means controlled by said first and second means responsive to any error signals produced by said comparing means for relatively adjusting said moisture removing means to remove moisture from said web so as to cause said actual moisture profile to conform more accurately to said desired moisture profile, said first signals constituting a group of three signals and said second signals constituting a group of three signals, said first means providing the first signal of said first group relating to actual gross moisture level and said fourth means providing the first signal of said second group relating to desired moisture level, said second means providing the signal of said first group relating to the skew of the actual profile and said fourth means providing the second signal of said second group relating to the skew of the desired profile, and said third means providing the third signal of said first group relating to the actual profile curvature and said fourth means providing the third signal of said second group relating to thE desired profile curvature. 